In the magnetic resonance imager, it is a practice to perform a delayed contrast-enhanced imaging that extracts a heart muscle in the form of a high signal region based on T1-enhanced imaging through utilization of the property a contrast agent, such as Gd-DTPA, is to aggregate on the heart muscle in the state of necrosis/infarction.
The application of a magnetic field in delayed contrast-enhanced imaging (pulse sequence, hereinafter referred merely to as sequence) is generally based on a procedure as per the following. Namely, after a wait time TD (first wait time) from the R-wave, an inversion recovery sequence is performed by stopping the patient's breath, to apply a slice-non-selective 180-degree-inversion pulse as a pre-saturation sequence synchronously with an electrocardiogram R-wave. Then, a signal-measuring sequence is performed to measure an echo signal after a wait time TI (second wait time) Generally, some 20 echo signals are measured per pulse. By repeating those over 10 to 20 pulses, imaging is made in about 15 seconds per slice.
However, in the delayed contrast-enhanced imaging, it is known that there arises, on the image, an artifact resulting from the ventricular blood. Such an artifact is responsible for the following. Namely, the blood relaxation time T1 is approximately 1500 ms at a static magnetic-field intensity 1.5 T, which is longer as compared to the usual cardiac cycle (from 700 ms to 1 second). In a delayed contrast-enhanced imaging, because inversion-recovery and signal-measuring sequences are performed on every pulse, the longitudinal-magnetization of blood is not fully recovered within the time period of one pulse. Consequently, there encounters the intensity variation of between the echo signals measured on respective pulses. As a result, an artifact occurs on the image reconstructed from the echo signals. Because the blood and the heart muscle are adjacent within the ventricle, the artifact on the image is superposed over the heart muscle, thus lowering the diagnosability.
The art described in (Patent Document 1) is known as a method to prevent the artifact. In the art, a first inversion recovery pulse is first applied to a predetermined slice synchronously with an electrocardiogram R-wave. Then, a second inversion recovery pulse with an notch is applied to a region except for the predetermined slice. Thereafter, an echo signal is measured as to a region included in the predetermined slice, as a slice plane. Namely, by applying twice inversion recovery pulses different in saturation region within a time period of one pulse, an artifact resulting from the intraventricular blood is prevented. This can obtain a sufficient suppression effect for the blood outside the predetermined slice, is described.    Patent Document 1: JP-A-2002-306450
In the delayed contrast-enhanced imaging, artifacts can arise from the intraventricular blood. However, in the art described in (Patent Document 1), the second inversion recovery pulse does not have an effect upon the blood included in the predetermined slice. Thus, there is obtained an insufficient effect in suppressing the intensity variation or the echo signals of from the predetermined slice. This results in an imperfect suppression against the artifact occurring on an image.